/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.common.io;

import java.io.IOException;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sss.common.DataReceiver;
import org.sss.mapreduce.Configuration;
import org.sss.mapreduce.DB;
import org.sss.mapreduce.GroupID;
import org.sss.mapreduce.SssException;
import org.sss.mapreduce.StorageNode;

/**
 * .
 * NOTE: This class used by only map operation.
 */
public class FlatDataReader extends AbstractFlatDataReader{
  @SuppressWarnings("unused")
  private static Logger logger = LoggerFactory.getLogger(FlatDataReader.class);

  public FlatDataReader(Configuration conf,
                        StorageNode node,
                        GroupID gid,
                        int subhash,
                        DataReceiver<List<byte[]>> next) throws SssException {
    super(conf, node, gid, subhash, next);
  }

  /**
   * .
   * NOTE: This method should NOT be called for TTDB with restricted access.
   */
  @Override
  protected void issueCommands(IOThread iot) throws SssException, IOException {
    DB db = iot.getDB(node);
    int limitNBytes = iot.getIOGetLimitNBytes();
    boolean initial = true;
    byte[] prefix   = KeyFormatter.getPrefix(getSource(), subhash);
    byte[] sentinel = KeyFormatter.getSentinel(getSource(), subhash);

    while (true) {
      checkCanceled();
      List<byte[]> kvs =
          isDestructiveRead() ? db.ranged(prefix, sentinel, limitNBytes, initial)
                              : db.range(prefix, sentinel, limitNBytes, initial);
      initial = false;
      final int count = kvs.size();
      countup(kvs);
      if (count > 0) {
        prefix = kvs.get(count - 2);
        next.put(kvs);
      } else {
        break;
      }
    }
    next.close();
  }
}
